Glaucoma is a disease condition of the eye in which increased intraocular pressure (IOP) is created by reduction or blockage of the drainage mechanism for the aqueous fluid produced in the anterior portion of the eye. Such conditions are usually treated by topical drugs in the form of eye drops, but may result in surgical treatment if drug treatment becomes ineffective or if patient compliance is an issue. Traditional glaucoma surgery, such as a trabeculotomy or trabeculectomy, involve dissection of the eye and the forming of new passages through or near the trabecular meshwork portion of the drainage pathway and directing the fluid to a subconjunctival pocket known as a bleb. Although effective for a short period, long-term follow-up of these treatments shows marked increases in intraocular pressure and therefore low success rates. Other serious complications include hypotony, in which too much drainage is accomplished and the IOP drops to sight threatening levels. These procedures also involve post surgical complications, such as infection and long-term issues related to bleb management.
A recently developed surgical treatment for glaucoma is known as viscocanalostomy. The procedure involves surgically opening a flap of the sclera and dissecting down to de-roof Schlemm's canal to increase aqueous humor drainage. A high viscosity viscoelastic material is injected into the canal to dilate it, and may act to open the trabecular meshwork from the canalicular space. The viscoelastic material may also act as a fibrosis inhibitor, reducing the influx of fibroblastic cells from the healing response, which would negate the effects of the procedure by blocking fluid flow. Stegmann, et al. in U.S. Pat. No. 5,486,165 discloses a microcannula designed for delivery of substances to Schlemm's canal during this procedure. In EP 089847, Grieshaber, et al. disclose an improvement to the Stegmann apparatus to deliver substances or stents for maintaining the passage of fluid in the canal.
Other surgical procedures, such as non-penetrating deep sclerectomy and trabeculectomy involve accessing and treating the aqueous drainage system in various manners. Minimally invasive access to the requisite tissues involved in aqueous fluid drainage, such as the trabecular meshwork, Schlemm's Canal, aqueous collector channels and aqueous veins can provide treatment with fewer complications.
The invention is directed at an ophthalmic microsurgical system comprised of a microcannula and associated microsurgical tools, which may be directly inserted into the sclera, Schlemm's Canal, aqueous collector channels, aqueous veins or other ocular tissues to allow minimally invasive access and progressive treatment with surgical materials and tools.
The following patent documents relate to methods and apparatus for treatment of glaucoma and other ocular diseases.    U.S. Pat. No. 5,360,399 METHOD AND APPARATUS FOR MAINTAINING THE NORMAL INTRAOCULAR PRESSURE, inventor Robert Stegmann    U.S. Pat. No. 5,486,165 METHOD AND APPLIANCE FOR MAINTAINING THE NATURAL INTRAOCULAR PRESSURE, inventor Robert Stegmann    U.S. Pat. No. 6,142,990 MEDICAL APPARATUS, ESPECIALLY FOR REDUCING INTRAOCULAR PRESSURE, inventor Reinhard O. W. Burk    WO 0064389 TRABECULOTOMY DEVICE AND METHOD FOR TREATING GLAUCOMA, inventors Brown Reay H, Lynch Mary G, King Spencer B III    WO 02/089699 MEDICAL DEVICE AND METHODS FOR USE FOR GLAUCOMA TREATMENT, inventors Tu Hosheng, Smedley Gregory, Niksch Barbara, Haffner David    WO 02/080811 GLAUCOMA STENT AND METHODS THEREOF FOR GLAUCOMA TREATMENT, inventors Tu Hosheng, Smedley Gregory, Niksch Barbara, Haffner David    WO 02/070045 GLAUCOMA TREATMENT DEVICE AND METHOD, inventors Brown David, Anderson Richard    U.S. Pat. No. 6,471,666 INJECTABLE GLAUCOMA DEVICE, inventor Odrich Steven    U.S. Pat. No. 6,464,724 STENT DEVICE AND METHOD FOR TREATING GLAUCOMA, inventors Lynch Mary, Brown Reay    WO 01/78656 DEVICE FOR GLAUCOMA TREATMENT AND METHODS THEREOF, inventor Hill Richard